Motor vehicle gearbox

ABSTRACT

In a motor vehicle transmission, in particular a multi-speed synchronized countershaft transmission, each two speeds are associated with one among several gearshift sets (28, 29). It is essential that the two speeds (1st and 3rd or 2nd and 4th) associated with each gearshift set are not successive speeds. The great advantage here is that the gearshifting thus obtained is a &#34;shifting-shifting&#34; system which makes it possible to carry out overlapping actuating operations and thus a reduction of the time interval between gearshifts. At certain speeds, several gearshift sets or synchronizing mechanisms can be simultaneously loaded whereby the load of the individual gearshift sets (28, 29) is substantially reduced. Great advantages such as shorter gearshifting times, longer service life of the synchronizing sets and smaller gearshift sets may thus be obtained.

The invention concerns a motor vehicle transmission, especially amulti-step synchronized transmission, according to the preamble of claim1.

In a multi-step motor vehicle transmission existing at present, twosuccessive or adjacent speeds are respectively associated with onegearshift set. By a first gear shift set consisting of, for instance, agearshift sleeve with or without synchronization, gearshift levers orshifting dogs, etc., the first and the second speeds, for instance, areengaged and disengaged while a second gearshift set engages anddisengages the third and fourth speeds, for instance, and possibly twoother speeds can be shifted via a third gearshift set. If, in such aknown transmission, the next higher or lower speed is engaged, aninterruption of the traction force occurs during the shifting operation,at least at low speeds, since a speed adjustment of the countershaftmust be effected via the synchronizing means of the next speed, forinstance, for the upshift. When changing from the first to the secondspeed, the synchronizing means of the second speed must effect a brakingof the corresponding gear and thus of the whole countershaft so as tomake possible the engagement. As result of this, a relatively severewear (high load) of the gearshift sets takes place, shortening theservice life thereof. Besides, an increased synchronization period isneeded whereby a long interruption of the traction force results due tothe time interval between gearshifts which may originate in the controlfrom the thrust operations during the gear-selection process and fromdead periods. To prevent such severe wear, for instance, thesynchronizing sets must be made relatively large.

The problem to be solved by the invention is to provide a motor vehicletransmission of the above mentioned kind which makes possiblesubstantially improved gearshifting properties combined with longerduration, especially of the synchronizing means, and practicalimprovements.

This problem is solved by a motor vehicle transmission which, accordingto the invention, has the features of claim 1. The sub-claims containother advantageous embodiments.

Accordingly, a novel gear arrangement is obtained, that is, the twospeeds associated with respective gearshift sets are not successivespeeds. Thus, for instance, speeds 1 and 3 are actuated by a firstgearshift set and speeds 2 and 4 by a second gearshift set, etc. Thisaffords the possibility, when changing speed for instance from the firstto the second or from the second to the third, of utilizing the separatecontrollability of the gearshift devices for reducing the time intervalbetween gearshifts, since adjacent speeds are actuated or shifted bydifferent gearshift sets or gearshift devices.

It is advantageous for this that an actuating means, driven andcontrolled independently of the actuating means of the remaininggearshift sets, be associated with each gearshift set. For this purpose,any actuating means known per se having different energies such ashydraulic, pneumatic or electric devices can obviously be used. But inmulti-step gearshift transmissions existing at present, the electricpower supply existing in each vehicle is being increasingly used assource of energy, in addition the trend being toward the electroniccontrol of the driving operations. Therefore, it is especiallyadvantageous to use a mechanism controlled and actuated by electricalpower such as an electromotor combined with an electronic control as anactuating means. For coverting the rotation movement, obtained by theelectromotor and controlled in relation to the torque and direction ofrotation, to a translatory gearshift movement any conveniently designeddevice which makes such conversion possible can be used. It is thuspossible to use, for instance, a spatial cam transmission like threadedspindle or ball and socket threaded spindle combined with acorresponding nut or a rack and pinion device, etc. Said actuating meansmakes very precise control of the translatory rotary movements for thegearshift sets of the transmission possible.

By virtue of the possibility of operating and controlling the actuatingmeans independently of each other, the gearshift operations can becontrolled so as to bring about an overlapping actuation of theconverters and thus of the gearshift sets. This reduces the timeintervals between gearshifts. This can be advantageously done especiallyby the fact that the synchronizing means of several gearshift sets canbe simultaneously loaded. This is always possible when at least a higher(lower) speed still is present when upshifting (downshifting). When ashift is made, for instance, from the first to the second speed, it ispossible at the same time, by actuating the gearshift set for the secondspeed, to load also the gearshift set of the third speed in order toreduce the velocity of the countershaft. Due to the braking or bringinginto contact of the gearshift set of the third speed in addition to thatof the second speed which is engaged, the load of the individual loadedgearshift sets diminishes. This brings considerable advantages such asshorter gearshift times, a longer service life of the gearshift sets andthe possibility of using smaller gearshift sets whereby a very economicdesign is altogether obtained.

Compared to the "selection shifting" of the prior art, by using thegearshift system of the invention, generally designated as a"shifting-shifting" system, overlapping gearshifts and thus a reductionof the time intervals between gearshifts become possible together withother related advantages.

The invention is explained in detail herebelow with the aid of anembodiment compared to an embodiment according to the prior art and withreference to the drawings. In the drawings:

FIG. 1 is a diagrammatic illustration of a four-speed transmissionaccording to a known embodiment/gear arrangement;

FIG. 2 is a diagrammatic illustration of a four-speed transmission withthe gear arrangement according to the invention; and

FIG. 3 is a basic operational structure of the gearshifting system of amotor vehicle transmission of the invention according to FIG. 2.

The motor vehicle transmission 10 of the prior art shown in FIG. 1 is amulti-step synchronized countershaft transmission (four speeds) of aclassical construction from which the transmission 11 of the invention,diagrammatically shown in FIG. 2, differs only by the arrangement of thegears in relation to the actuating means 12, 13.

Thus, in the arrangement of FIG. 1 according to the prior art, twosuccessive speeds are associated with each actuating means 12, 13, thatis, the actuating means 12 operates the first and second speeds whilethe third and fourth speeds are actuated by the actuating means 13.

In the transmission of FIG. 2, according to the invention, non-adjacentspeeds are respectively associated with one actuating means 12, 13, thatis, the first and second speeds with the first actuating means 12 whilethe second actuating means 13 operates the second and fourth speeds.

Both the transmission known already and the transmission which is theobject of the invention fundamentally consist of a housing 14 having oneinput shaft 15, situated therein, co-axially with an output shaft 16 towhich is added paraxially offset a countershaft 17. The rotary movementassumed by the input shaft 15 is transmitted via the fixed gears 18 and19 to the countershaft 17 upon which are provided, depending on thenumber of speeds, additional gears 20, 21 and 22 corresponding to speedsone through three. The fourth speed is obtained by direct coupling ofthe input shaft 15 with the output shaft 16.

Gearshift sleeves 23 and 24, operatively connected with the respectiveactuating means 12 and 13, are non-rotatably but axially displaceablyprovided on the output shaft 16 and the idle gears 25, 26 and 27 for thefirst, second and third speeds, respectively, are additionally situatedon the output shaft 16 and each operatively connected with therespective gears 22, 21 and 20 of the countershaft 17. A gearshift set28 or 29, each consisting of the corresponding gearshift sleeve 23 or24, a part provided on the corresponding idle gear and on the inputshaft 15 and the respective synchronizing means, is associated with eachpair of gears.

Herebelow the operations of the transmission, according to the inventionwith the special help of the illustration of FIG. 2, are described.

In the illustrations on FIGS. 1 and 2, both actuating means 12 and 13are in a neutral position, that is, no speed is engaged. Upon drivingthe vehicle, the first speed is engaged via the actuating means 12whereby the transmission of movement or force occurs from the inputshaft 15 to the output shaft 16 via the gear pair 18, 19, thecountershaft 17, the gear pair 22, 25, the right coupling andsynchronizing means of the gearshift set 28 and the gearshift sleeve 23.

If a shift from first to second speed is now desired, the gearshiftsleeve 23 is disengaged from the idle gear 25 of the first speed by theactuating means 12, for instance, after control of the correspondingengine and of the linear device of the actuating means (not shown here)and is brought to the neutral position shown in the drawing.Simultaneously or shortly thereafter, the gearshift sleeve 24 is moved,via the second actuating means 13, away from its neutral position towardthe idle gear 27 of the second speed. At the same time the synchronizingmeans of the gearshift set 29 begins to grip and effects a speedadjustment of the gear 27 with the gearshift sleeve 24 or the outputshaft 16 until the corresponding clutch gears can be brought toengagement.

At the same time, with the beginning of the gearshift movement by theactuating means 13, the possibility of moving the actuating means 12from the neutral position assumed, after disengagement from the firstspeed, to the idle gear 26 of the third speed exists. Thereby thegearshift set 28 is loaded and likewise contributes to the speedadjustment of the countershaft. By virtue of the practicallysimultaneous loading of the two gearshift sets 28 and 29 of the secondand third speeds, the necessary loading of each one of the gearshiftsets becomes considerably reduced whereby the constructional costthereof accordingly can be kept lower.

The same overlapping actuation of both actuating means 12, 13 can beaccomplished when shifting from the second to the third speed, taking upfor support of the gearshift set 28 when the third speed is engaged viathe actuating means 12 of the third speed, the gearshift set 29 of thefourth speed by actuation thereof via the actuating means 13.

In the same manner, when downshifting from the fourth to the third speedor from the third to the second speed, the gearshift set of the secondor of the first speed, respectively, can be used as support.

The basic operational structure of a gearshift system for thetransmission according to the invention, shown in FIG. 3, is designedfor a six-speed transmission and not for a four-speed transmission likein FIGS. 1 and 2. But it can be clearly understood that in a four-speedtransmission as there are only two gearshift sets only two branches areneeded.

The basic operational structure shown takes into consideration that:

a. the electric energy must be converted to mechanical energy,

b. a translatory adjusting movement must be produced,

c. the adjustment movement must be produced in several, spatiallydifferent places and be available separately of each other,

d. the adjusting movement must be reversible,

e. the gearshift mechanism must be disengageable and engageable,

f. the actual adjusting position must be recognizable/detectable by anelectric signal, and

g. the adjusting movement must be controllable and regulatable(regulating distance, force).

From the diagram it is to be understood that the electric energy (U, I)used in 32, which is for branching, is divided, for instance, by meansof an electric clamping device into a number of branches correspondingto the number of actuating means. In each branch is effected, at 33, 34,35, a coupling/uncoupling by means, for instance, an adequate actuatorwhich processes the input/output signals 42, 43, 44. In a furtherdevelopment, a conversion occurs (U, I in ρ, M) at 36, 37 or 38 by arespective electromotor, there simultaneously flowing in a torquecontrol 45, 46 and 47 and a control 48, 49 and 50 of the direction ofrotation. The rotary movements obtained hereby are then respectivelyconverted by conversion (ρ, M in x, F), for instance, via a lineardevice such as threaded spindle with a nut, or a spatial cam geartransmission, all of which are diagrammatically represented by 39, 40,41, in a corresponding translatory adjusting movement for thecorresponding actuating means 12 or 13. Consequently, as alreadymentioned in the beginning, a separate control takes place for eachactuating means which makes an overlapping activity of the actuatingmeans possible and thus of the gearshift sets.

List of Reference Numerals

10 motor vehicle transmission of the prior art

11 motor vehicle transmission of the invention

12 first actuating means

13 second actuating means

14 housing

15 input shaft

16 output shaft

17 countershaft

18 gear

19 gear

20 gear

21 gear

22 gear

23 gearshift sleeve

24 gearshift sleeve

25 idle gear 1st speed

26 idle gear 2nd speed

27 idle gear 3rd speed

28 gearshift set

29 gearshift set

32 branching (clamp)

33 coupling/uncoupling (switches)

34 coupling/uncoupling

35 coupling/uncoupling

36 converting (electromotor)

37 converting (electromotor)

38 converting (electromotor)

39 converting (linear device)

40 converting (linear device)

41 converting (linear device)

42 in/output signal

43 in/output signal

44 in/output signal

45 torque control

46 torque control

47 torque control

48 control of direction of rotation

49 control of direction of rotation

50 control of direction of rotation

We claim:
 1. A synchronized countershaft motor vehicle transmissioncomprising:a plurality of gearshift sets (28, 29) each having asynchronizing device; a plurality of speeds (1 and 3 or 2 and 4)adjacently associated with each of said plurality of gearshift sets (28,29), with successive speeds of said transmission being associated withdifferent ones of said plurality of gearshift sets (28, 29); and anactuating device (12, 13) being associated with each said gearshift set(28, 29) for engaging a desired one of said adjacently associatedspeeds; wherein each said actuating device (12, 13) is controlled andoperated independently of one another in a manner such that thesynchronizing devices of said plurality of gearshift sets (28, 29) aresimultaneously loaded.
 2. A synchronized countershaft motor vehicletransmission comprising:a plurality of gearshift sets (28, 29) eachhaving a synchronizing device; a plurality of speeds (1 and 3 or 2 and4) adjacently associated with each of said plurality of gearshift sets(28, 29), with successive speeds of said transmission being associatedwith different ones of said plurality of gearshift sets (28, 29); and anactuating device (12, 13) being associated with each said gearshift set(28, 29) for engaging a desired one of said adjacently associated speedsas desired; wherein each said actuating device (12, 13) is controlledand operated independently of one another in a manner such that thesynchronizing devices of said plurality of gearshift sets (28, 29) aresimultaneously loaded; and each said actuating mechanism has anelectromotor combined with an electronic control for facilitatingcontrol of said actuating mechanism.
 3. A synchronized countershaftmotor vehicle transmission comprising:a plurality of gearshift sets (28,29) each having a synchronizing device; a plurality of speeds (1 and 3or 2 and 4) adjacently associated with each of said plurality ofgearshift sets (28, 29), with successive speeds of said transmissionbeing associated with different ones of said plurality of gearshift sets(28, 29); and an actuating device (12, 13) being associated with eachsaid gearshift set (28, 29) for engaging a desired one of saidadjacently associated speeds as desired; wherein each said actuatingdevice (12, 13) is controlled and operated independently of one anotherin a manner such that the synchronizing devices of said plurality ofgearshift sets (28, 29) are simultaneously loaded; each said actuatingmechanism has an electromotor combined with an electronic control forfacilitating control of said actuating mechanism; and a linear device isconnected to said electromotor for converting rotational movement ofsaid electromotor into translatory gearshift movement for actuating adesired one of said gearshift sets (28, 29).
 4. A synchronizedcountershaft motor vehicle transmission according to claim 3 whereinsaid linear device comprises a spatial cam gear transmission.
 5. Asynchronized countershaft motor vehicle transmission according to claim3 wherein said linear device comprises a threaded spindle and arotatable nut on said threaded spindle.